Dresden 2017 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 60: Magnetic Materials: Applications and Multielement Bulk Materials

MA 60.5: Vortrag

Freitag, 24. März 2017, 10:30–10:45, HSZ 101

Thermal and thermoelectric high-magnetic-field study of the multiband superconductor FeSe — •Stevan Arsenijević1, Tatsuya Watashige2, Lars Opherden1, Shigeru Kasahara2, Yoshifumi Tokiwa2, Yuichi Kasahara2, Takasada Shibauchi3, Hilbert von Löhneysen4, Jochen Wosnitza1, and Yuji Matsuda21Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany — 2Department of Physics, Kyoto University, Kyoto 606-8502, Japan — 3Department of Advanced Materials Science, University of Tokyo, Chiba 277-8561, Japan — 4Physikalisches Institut, Karlsruhe Institut für Technologie, 76131 Karlsruhe, Germany

We explored the high-magnetic-field behavior of the thermoelectric and thermal-transport coefficients to probe the quasiparticle excitations in the normal and superconducting phase of FeSe. The small and compensated thermoelectric coefficients increase with decreasing temperature (T) due to the T-dependent increase of the charge-carrier mobility and the dominant role of the small hole Fermi-surface pocket. The measured longitudinal and transverse thermal conductivities imply that a highly anisotropic small superconducting gap forms at the electron pocket whereas an isotropic and larger gap forms at the hole pocket. Below 1 K, both thermal conductivities exhibit anomalies at the upper critical field, Hc2, and at a constant field H* around 14 T. These results support the existence of a distinct field-induced superconducting phase above H* which emerges with a presumed large spin-imbalance of the hole Fermi-surface pocket.

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